Locking mechanism for door SGD-R25

Thanks for contacting us. We did sell this lock lever by itself at one time, but I'm afraid we're no longer able to supply it separately. We can only provide the complete handle set, which looks like our 82-033.

If the thumb lever shears off like you describe, then the issue is usually with the mortise lock. You may want to consider replacing that, as well. See our 82-218, this looks like it matches your hardware.